In conventional elevator installations the elevator cage and a counterweight are connected together by way of several cables or belts. The counterweight and the cage are supported and, as a rule, also moved by the cables or belts. For this purpose, drive force generated by a drive is transmitted by way of a drive pulley to the cables or belts. When the drive pulley rotates, the cable or the belt is guided over the drive pulley and thus raises or lowers the elevator cage or counterweight. In this connection, the drive moment is imposed under friction couple on the respective cable or belt section lying on the drive pulley over the looping angle.
In order to ensure a force transmission which is as efficient as possible, selection can be made of materials with a high co-efficient of friction which can be used not only on the drive pulley, but also as cable material. In addition, good guidance of the cable or belt and an efficient transmission of force are achieved by a drive pulley which follows a contour of the cable or belt so that large parts of the cable or belt surface are in contact with the drive pulley. For this purpose the surface shapes of the cable and the drive pulley have to be precisely matched to one another, since otherwise different pressures of the drive pulley on the cable of the belt occur, whereby different material loads arise in the cable or belt and therefore different levels of wear phenomena.
Moreover, in the case of different loading a uniform transmission of force to the cable or belt is not possible, so that in certain circumstances lateral forces or shear forces arise which can lead to cable torsion or cable unraveling phenomena, which in turn disrupt the cable structure in terms of its balance. Twist phenomena of that kind can occur particularly when the drive pulley or cable rollers are arranged at an angle.
A cable with two tensile carriers in an elastomeric casing is known from EP 1 061 172, wherein the elastomeric casing has an outer contour which co-operates with corresponding grooves in the drive pulley. Specifically, the cable is held by a rib, which is formed in cable longitudinal direction, in co-operation with a guide groove shape, which is provided to be complementary therewith, on the drive pulley in the track.